Opal basil: the purple basil with a spicier oil, in bunches year-round

Opal basil is sweet basil's purple cousin: the same species, a darker leaf, and a flavor with more spice and anise behind the sweetness. It is the basil chefs reach for when a plate needs color and bartenders reach for when a syrup or vinegar needs a tint. King Quality Produce carries opal basil year-round, packed 60 bunches to a box. This guide covers what it is, where it comes from, how to buy and store it, and what research says about the purple leaf.

What opal basil is

Opal basil, also sold as red or purple basil, is a group of purple-leaved cultivars of Ocimum basilicum. Dark Opal is the original named variety, and Purple Ruffles and Red Rubin are the others you will see on a seed list. A UC Davis production summary describes Dark Opal and Purple Ruffles as intermediate in plant size between the big Italian types and the small bush types, with purple flowers and only slight differences in flavor between them⁶. Purdue's 1985 production guide filed purple-foliage types such as Dark Opal under ornamentals⁷, which tells you how far the culinary trade has come: today the purple leaf is a plating staple.

The flavor difference is in the oil. A 2017 analysis of basil essential oils found that purple basil (O. basilicum var. purpureum) was dominated by methyl chavicol at 57.3 percent of the oil, with linalool second at about 18 percent, where the green variety in the same study was 68 percent linalool⁵. Methyl chavicol is the anise-like compound, which is why opal basil reads spicier and less floral than Genovese; our customers describe it as a clove-like edge. The color comes from anthocyanin pigments in the leaf, part of the same family of phenolic compounds that gives purple basils their higher antioxidant readings in the lab⁴.

Where and when it grows

Basil is a warm-season crop that grows best between 45 and 80°F and dies at frost, and commercial U.S. production is concentrated in Arizona, California, Florida, New Mexico and North Carolina, with Mexico a large exporter to the U.S. market⁶. Opal basil follows the same calendar as sweet basil but in much smaller plantings, and KQP sources it from growers in Mexico, the Southwest and California so that it is on our list every week of the year.

Because volumes are small, availability depends on a handful of growers staying in production through the cool months. Our year-round program is built on that, but the box count for purple basil is a fraction of green basil, so order ahead for a large event rather than counting on the floor.

How to buy opal basil: bunches and receiving

Opal basil comes in bunches, 60 bunches to a box, and we quote by the box. Growers harvest before bloom, in the cool part of the day, and keep bunches loose so air can move through them³. UC Davis's quality indices for culinary herbs apply: freshness, uniform size, form and color, freedom from yellowed or damaged leaves, decay, insect damage and wilting, and a strong characteristic aroma².

Purple basil has one receiving problem green basil does not: you cannot easily see cold damage. Chilling injury on basil shows as blackened leaves, stem discoloration and lost aroma³, or as browning of the leaves and growing tip, bronzing of the veins and loss of gloss², and on a purple leaf the browning and blackening hide in the color. Check the stems instead, which should be firm and clean rather than dark and soft, run a thumb over the leaves for the gloss, and smell the box. A purple bunch that has lost its aroma has been chilled, whatever it looks like. Leaf color varies from deep purple to purple flecked with green from bunch to bunch; judge the box on freshness and aroma rather than on an even color.

• Smell first: no aroma means it was chilled
• Stems firm and clean, not dark or soft
• Leaves glossy, not dull or bronzed along the veins
• No wilting or slimy leaves in the center of the bunch
• Bunches loose in the box, not packed tight and wet

Storage and shelf life

Opal basil stores like all basil, which is to say unlike almost every other herb. UC Davis recommends 32°F for most culinary herbs but says basil is chilling sensitive and should be stored above 50°F at a relative humidity above 95 percent, with one to two weeks of shelf life depending on water loss². Rutgers puts the optimum at 55°F with 90 to 95 percent relative humidity and cites UC Davis work in which basil held at 50 to 68°F for ten days kept markedly better visual quality than basil at 32°F³.

Keep bunches loose, stand the stems in water or cover them loosely, and never let the leaves touch ice³. Basil is minimally affected by ethylene, so it can share a room with ripening fruit; what it cannot share is a 34°F walk-in with the lettuce². Storage at chilling temperatures greatly reduces basil's aroma quality, and aroma declines over time even in good storage², so buy the week's needs rather than the month's.

Nutrition by the numbers, and what the lab says about purple

USDA FoodData Central does not separate purple basil from green; its entry for fresh basil reports, per 100 g, 23 calories, 92.1 g water, 3.15 g protein, 1.6 g fiber, 177 mg calcium, 3.17 mg iron, 64 mg magnesium, 295 mg potassium, 1.15 mg manganese, 18 mg vitamin C, 68 µg folate, 264 µg vitamin A (RAE), 3,142 µg beta-carotene, 5,650 µg lutein plus zeaxanthin and 414.8 µg vitamin K¹. Against FDA's Daily Values of 120 µg for vitamin K and 2.3 mg for manganese⁸, 100 g of basil carries more than three times a day's vitamin K and about half a day's manganese; a garnish is a small fraction of that.

Where purple basil stands apart is phenolic content. In a 2002 Rutgers study of basil extracts, purple basils measured 81.7 to 126.2 mg of total phenolics (as gallic acid equivalents) per gram of dry leaf against 35.6 to 62.9 mg for green basils, and their antioxidant activity ran higher in both assays used, with Dark Opal posting the highest phenolic content of any cultivar tested at 126.2 mg⁴. The authors attributed the activity to non-volatile phenolics, including flavonoids and anthocyanins, rather than to the essential oil, which contributed under 6 percent⁴. That makes opal basil rich in phenolic compounds relative to green basil. It is a measurement, not a treatment claim, and a leaf on a plate is still a garnish.

In the kitchen: how Los Angeles uses opal basil

Plating is the first use. A purple leaf on a caprese, a burrata plate or a tomato salad does what a green one cannot, and the spicier flavor stands up to stone fruit, melon and aged balsamic. Bars and pastry kitchens infuse it: a syrup or vinegar steeped with opal basil takes on a pink-to-magenta color along with the anise note, which is why cocktail programs and dessert menus around the city keep it on the order.

The color leaches into liquids and darkens when cooked, so use it raw or as a finishing infusion. At the market, keep it out of the misted case and off the ice, and merchandise it next to tomatoes and mozzarella rather than in the herb rack, where it gets lost.

Opal basil is on our list year-round, and bunch size and counts change with the growing regions week to week. Call the office at (213) 627-7181 or email office@kingqualityproduce.com for this week's availability.